1. Field of the Invention
This invention relates to the field of preparing textile fabrics for subsequent dyeing and finishing steps. In particular, the invention relates to a novel method for desizing, scouring, bleaching and mercerizing such fabrics.
2. Description of the Prior Art
Conventionally, in the weaving and knitting of textile fibers into fabrics, coatings, e.g., size, are applied to the fiber to facilitate the handling thereof in the weaving and knitting procedures. This size must be removed prior to subsequent treatment of the fabric. In addition, desizing operations are usually carried out in conjunction with either scouring, i.e., cleaning with alkaline agents, bleaching, usually with peroxides, and/or mercerizing, of the fabric in order to whiten the fabric and remove wax therefrom.
In the past, each of these processes, i.e., desizing, scouring, bleaching and mercerizing, was carried out using appropriate agents either dissolved or dispersed in a liquid medium, e.g., water or an organic solvent. This results in the problem that relatively large amounts of liquid medium must be removed from the fabric after the operation. Consequently, a substantial amount of the cost incurred in such processes resides in the liquid medium removal step.
Such liquid media present a further problem in that after they are removed, they must either be disposed of or recovered for reuse. In the case of an aqueous treatment system wherein the liquid medium is water, the water is normally disposed of as waste. In recent years, the environmental problems that related to the disposal of water with residual chemical agents therein have become increasingly important.
With respect to organic solvents as the liquid medium, it is normally desirable to recover them because of the relatively high cost. Obviously, such recovery systems only add to the expense of the overall treatment process. Moreover, disposal of the solvent, if it is desired not to recover it, also presents environmental problems.
The foregoing problems become even more severe when textile fabrics which are highly absorbent are treated. Additionally, because of the relatively large absorption of the liquid, the weight of the wet fabric which is being handled increases significantly, and often results in processing problems and increased expense.
Methods have been developed wherein various types of treating agents, e.g., dyes, anti-crease agents, etc., can be applied to fabrics in the form of a foam. Such methods are directed to avoidance of the problems depicted above in connection with liquid removal. In particular, reference is made to U.S. Pat. Nos. 4,118,526, 4,193,762, 4,208,173, 4,266,976, 4,270,915, 4,282,729 and 4,299,591, the contents of each of which being hereby incorporated by reference.